Manufacture of transparentized sheets for drawing, tracing, and copy reproduction



Pmmea July 6, 1943 UNITED STATES MANUFACTURE OF 1 PATENT FF ETRANSPARENTIZED SHEETS FOR DRAWING, TRACING, AND COPY REPRODUCTION Y 7Walker M. Hin'man; -Winnetka, and Walter G. 5

' Hollmann, Chicago, 111., assignors to The Frederick Post Company,Chicago, 111., 'a corpora-' tion of Illinois No Drawing. Applicationrulys, 1939, "Serial No.283,376

23 Claims. (cam-1 43 j v The present invention relate to tracing sheetsas of cloth or paper, such as is used to receive ink, pencil or printingmarks, or other images, commonly desired to provide a.light-transmitting figured sheet for use in reproducing copies 51 by alight-printing process.

Light-transmissibility'is a requirement. Tracing cloth is the morecommon article of this class.

starch or gelatin or like hydrophili substance, containing emulsifiedwaxes or oils, or "other transparentizing agents, patticularly vegetableoils. It is actually translucent rather than transparent, although"transparency is referred toin relative terms, such as more transparentor less transparent instead of less translucent? and more translucent.This is because it is opaque to dis tant objects, and translucent tolight, but transparent to images in surfacecontact withthe sheet. Indiscussing the-present invention the term transparent? will beused withthe meaning above indicated.

A requirement of present day tracing cloth is 25 a matt drawing face toavoid gloss. Usually, the back has gloss to prevent accumulation ofdirt. The face also must receive and hold ink or pencil or rinting. Itmust also withstand erasure. It

is desirable that, it be semi-waterproof to such extent that ink doesnot penetrate into the cloth, thus to permit erasing without destroyingthe cloth. and to such extent that moisture from the hands does notinjure it.

These requirements of the face may be met by a special coating on theface. The coating may vary according to special uses. One coating mayproduc a good cloth for pencil and a poor cloth for ink, and another mayproduce a good cloth for ink and a poor cloth for pencil. Such coatingtreatments heretofore have lessened the transparency by r ason of theadded coat. This is commonly effected by applying some sort of alacquer. used. A grit or abrasive has also been included in such coatingto give a good matt surface.- However, the addition of such grit takesaway from the transparency and this limits the amount 'of grit which canbe practically included.

We have observed that when an ordinary tracing cloth is coated with alacquer without a grit, its transparency is reduced, and that thetransparericy is further reduced in aging of the freshly lacqueredcloth. We have studied this change,

have found the cause of it, and have supplied a remedy. We have alsofound that the remedy is useful in producing tracing sheets from otherbasic sheet materials, such as an ordinary sheet of paper, and that itsuse is not limited to opera- It is usually a fine grade of woven linen,or long staple cotton, or a mixture, filled with 10 in common parlance15 A cellulose derivative base is commonly 45 tions on tracing clothcontaining a transparentizingage'nt. It is an object of the presentinvention-to produce a transparenttracing sheet.

It is another object oftheinvention to convert sheet material such ascloth" or paper into a transparent sheet useful for tracings.

It-is a further objectoftheinvention tocoat,

an ordinary tracing cloth having a transparentize ing agent so as toimprove its face without lessening the transparency of-the-clothitself,orwith improvement of the transparency of-the cloth itself. m

It is a still further object of the invention to coat anordinary'tracing cloth with-a coating composition which provides a;coat. not perfectly transparent, and to obtain :a coatedproduct having atransparency greater. than the uncoated cloth. I 1

Another object of the invention is the provision of a coating on.tracing cloth which provides a matt face improved for both pencil andink.-

- Another object of the invention i to a tracing cloth sotransparentized-that the weave the following description and explanationof the 1 invention.

In experimenting with-various coatings on common tracing cloth, wehave'discovered that applied solutions of coating ,material are ,ca-

pable of extracting transparentizing ;material from the body of thecloth into the coating. We have found-that the solvent in; the coatingcomposition does this,.and further,;that, after the solvent has beenevaporated, the migration of transparentizingagent ,from the cloth tothe coating continues. The transparency of the body of the clothisactually, lowered even though the coating itself be. perfectlytransparent. However, where the coating has of necessity been'slightlytranslucent by reason of some inclusion therein, the transparencyobtainedhas been reduced by two factors, namely the extraction oftransparent-izing materialfrom the cloth, and the superimposition-of alight-obstructing coating. 'By means of the present inventionfwe mayadd'a light -obstructing coating with less orno loss, or even withimprovement in the transparency of the cloth body itself;

We have been able to coat a tracing cloth with a light-obstructivecoating and produce a coated clot-h more transparent than the uncoatedcloth.

We accomplish our purpose in one way by using a coating solution whichhas its solvent power for the transparentizing agents of the clothpartially or wholly satisfied. We may produce transparency by using acoating solution which on drying yields a transparentizing. agent to thecloth. The process may be more mixed than above indicated. .For example,the coating solution or resulting film may extract some of thetransparentizing agent from the cloth, and at the same time yield to thecloth the same or a different transparentizing material added to thecoating for that purpose. Whether the final coated cloth, compared tothe uncoated clot-h,

has more, or less, or the same transparency, depends entirely upon themanner in which the present invention is carried out. We prefer,obviously, tocarry out the invention to secure a coated cloth whichismore transparent after coating than before, and .hence illustrateourinvention by a preferred procedure which accomplishessuch purpose.

However, it is to be understood that our invention is not limited tocoating prepared tracing cloths on the market, which already contain atransparentizing agent. Our preferred procedure ofusing a, coatingcomposition which readily yields a transparentizing agent, may be usedto coat a paper or cloth, or other such sheet capable of being.transparentized, to yield said agent to the sheet coated, thus totransparentize it as well as coat it.

Thus, in either case, we obtain a tracing sheet which has atransparentized body and a transparentcoating, each containing atransparentizing agent for the body, whereby there is a balance offorces, one tending to cause migration of the agent from the body intothe coat,' 'and the other'tending to cause migration of said agent fromthe coating into the body, or providing a partial or complete saturationof the film so as to prevent some migration from the body to the coat.

In the trade the tracing sheets provided (commonly of cloth) areprimarily intendedto receive ink, but in those special cases where theyhave been specially treated to serve also in some acceptable degree forpencil, they, are termed pencilcloths.

Heretofore, pencil cloths have been of such grade as to limit their useto pencils of hardness H or 2K, in order to secure a satisfactorydensity to the line drawn. The inclusion of grit for tooth need not belimited by requirements for transparency.- Accordingto our invention, wemay produce a coated cloth for pencil which is more transparent than theuncoated cloth, and which permits of sufiicientgrit so that it will takea pencil of 4H to 6H. Draftsmen prefer such harder pencils, because theymake finer tions) of penciling a tracing and then inking over, or firstpenciling onto drawing paper, and then inking onto a tracing clothplaced over the penciled paper.

The trade prefers a tracing cloth rather than a tracing paper becausethe woven base gives strength and assurance against damage or tearforsuch use, and as permanent records.

process and is carried on by but a few manufaclines, but heretofore theyhave not been able to use them because the line was not sufficientlyturing sources. The resulting cloth has heretofore been employed for thereceipt of a coating containing grit, to improve its surface, asdescribed in British Patent No. 483,011 to Paul Koenig. In carrying outour invention we may begin with any original commercial "tracingcloths.!..,,We may also use our invention on any suitablefilledclotheven though lthas no transparentizing: agent in the filling. In suchcase, our process provides the transparentizing agent. For example wemay use our invention on the following commercial tracing cloths whichare already transparentized but not lacquered or otherwise coated overthe filling material.

Imperial, Winterbottom Book Cloth Co., Ltd.,

Manchester, England.

Excelsior, Winterbottom Book Cloth Co., Ltd.,

Manchester, England.-

Arkwrightf' Arkwright Finishing Co., Providence,Rhod e Island.

Prudence, Arkwright Finishing Co., Providence, Rhode Island.

Kosmo Spezial, Richard Schwlkert. Freiburg, Breisgan, Germany. 1

.(No mark), J. Landauer, Braunschweig, Germany.

We may also use it on paper, a desired requirement of which is that itis not sized or filled with mineral filler which will add to opacity.Such paper may be absorptive of the coating composition canon-absorptiveof it," so long as there is good adherence of the resulting film. Ourpreferred coating readily exudes the transparentizing agent into thepaper, and apparently with considerable force Where there is a goodinterface by good anchorage.

In carrying out our invention in its preferred manner, 'we do not needto know the identity of the transparentizing. agents in atransparentized filled tracing cloth. In the trade, the basic item"sider the constituents of the cloth, but having" the knowledge that atransparentizing agent is extracted by a coating solution we'use acoating solution which has a transparentizing property for the filledcloth, in order to compensate for any detransparentizing effect, whichthe same composition might have. The latter effect may readily bedetermined by omitting the transparentizing agent which we add to ourcomposition. We prefer to make the transparentizing effect greater thanthe detransparentizing effect, but this is not always necessary. Wherewe use but one coat, we must also consider the effect of the coatingcomposition on the drawing surface, as well as upon the cloth.

We have found that by using a coating solution containing atransparentizing agent, the coating as applied, or as it dries, canshare such agent with the cloth. The cloth also may share itstransparentizing agent with the' coating.

Therefore, we prefer to use" enough agent to get a net improvement intransparency. However, we may use less than this amount and secure nochange, or some loss in transparency, yet an improvement over use of acoating without a transparentizing agent to be shared by the cloth,

The character of the coating solution may vary widely, and commonly itembodies a solid base such as a cellulose derivative, bases, in avolatile solvent with plasticizer for giving flexibility. base requiresa plasticizer therefor. We find that those plasticizers which are oilyor liquid are also transparentizing agents. These may be synthetic, suchas dibutylphthalate, or natural, such as caster or other vegetable oilsand mineral oil. We may use a non-transparentizing agent as plasticizer,such as some of the alkyl sulfonamides,

and use a tran'sparentizing oil in addition, which,

may have some additional plasticizing. property. Plasticizers may besolvent plasticizer or non-solvent plasticizer. The former has a solventpower for the base plasticized, while the latter does not,

and is mechanically held or dissolved in the base plasticized. Castoroil and mineral oil are nonsolvent plasticizers for nitrocellulose, andif an excessive quantity is used as a plasticizer, the excess isrejected by exudation. It is this effect which is desired in thisinvention. Hence we use a transparentizing agent which isrejected, andits function as a plasticizer is only incidental. If the amountretained. is not sufficiently plasticizing we may add other plasticizer.This may or may not add to the transparentizing action. Where it is asolvent plasticizer it i less likely to exert a transparentizing actionbecause the affinity for the base to hold it'is greater than thetendency to reject it and the tendency of the sheet to absorb makes thecoating more thermoplastic, and subject to sticking to another surface,especially a like surface.

Where the transparentizing plasticizer is highly compatible with thebase of the lacquer it is retained by the liquid lacquer and by thefilmfrom the lacquer, and is not readily shared with the cloth, if atall, for the purpose of transparentizing it. For example, castor oilwhich is anon-solvent plasticizer for nitrocellulose, is normally a goodtransparentizing agent for the cloth, but it is too highly retained bythe lacquer to be given up to the cloth. This is true of dibutylphthalate and other solvent plasticizers. Hence, where we want the agentto be yielded to the cloth it must be one which in the quantity present,is not readily held by thefilm on drying or when dried. We therefore usea transparentizing agent which the film tends to reject, thus increasingthe relative claim for it by the cloth. Because we use such a.rejectable agent for transparentizing, some of it may be left in theresulting coating as a plasticizer. This permits having solventplasticizer,

it. Too much solvent plasticizer.

where it may be desired. However, by depending upon the retained agentas plasticizer and by not using solvent plasticizer," we produce astickproof cloth. We prefer to use mineral oil as our transparentizingagent fora nitrocellulose base lacquer, because it has a limitedsolubility in a dried nitrocellulosecoating, and because it is or amixture of For example a nitro-cellulose liquid, and readily exudedunder normal conditions. Thereisa tendency for mineral oil dissolved'incommon with nitrocellulose'in a solution to exude as the solvent'driesaway.- This tendency to exude is augmented by contact with the tracingcloth to absorb it, thus transparentizing the cloth. The use of too muchoil may of course cause some exudation at the drawing surface, whichshould not be undulyoily. The effect of this tendency will be discussedlater.

v For the drawing surface for pencil, there must be a tooth. This isaccomplished mechanically by including a gritor like substance. This isan additional inclusion in a lacquer coating which renders the coat lesstransparent than without it. It is an opaquing" agent, the effect ofwhich reduces the benefits of including a transparentizing agent tobenefit the body of the cloth or paper. secure greater transparency inthe coated body sheet than in the uncoated sheet, in spite of theopaquing effect of the grit.

The gri may be any solid substance,-preferably a transparent mineralpowder, and it may be chosen to have anxindex of refraction near that ofthe coating to render it less "opaquing." Because bonate, barytes andothers. One reason for preferring silica is that it is' highlytransmissive of ultraviolet light, which is a highly actinic componentof the light rays used in reproducing copies such as blueprints anddiazotypes.

We also prefer to coat but one side of the tracing cloth, or of paper.This has a real advantage in commercial handling of the material. Asmade, the coated material is rolled for storage, shipment and sale. Thisbrings the coated'face against the uncoated face. The latter readilyabsorbs 'anyoil on the drawing surface present before rolling, or exudedwhile in the roll. Thus at the time of use, the surface is not oily.

We are not limited to coating but one face and may coat both faces.However, where we make such a change and use the same or similarsolution on both sides, we reduce the amount of 'transparentizing agentin the composition by nearly one-half, because it enters the cloth fromboth sides. This reduces the amount present to 'be exuded at thesurface, to such an extent that is an advantageous requirement because acoat- However, the invention may be used to I For example, we maytracing cloth as well as to the drawing face.

Although we have describedthe inventiongen erally and inits preferredaspect, as involving only one coating to provide a drawing surface, andto transparentize, or to prevent extraction or transparentizing agentwhere it ispresentit is to be understood that this does not limit theinvention. The described applied coat maybe a first film or underfilm,on which another may be depo fdesired. The invention may be carried out;ytco'ating the glossy back of ordinary tracing cloth with atransparentizing. or a non-detransparentizing composition, withoutaltering the drawing face of the cloth. Both surfaces may be coated toprovide two drawing facesror the sheet. Numerous changes andmodifications of the invention may be practiced.

use a coating according to thisinvention, but lacking grit, which willdry to a quite oily surface. Upon this we may apply another coatingwithout any transparentizing agent, but carrying grit, to provide anonolly drawing surface. r

Furthermore; "we may make a tracing sheet from paper byiapplying to asheet of paper a lacquer composition, such as in Example 1, omitting thegrit, to provide a glossy waterproof back and to transparentize thepaper, and use the uncoated side of the paper for the drawing surface.Or this' drawingface may be coated with the same compositioncontainingthe grit. Theuse of alarge amount ofabrasive gives excellenceas a pencil cloth. This makes it unnecessary to press down onthe clothto eflect a heavy line. Heretofore such pressing was necessary, and thephysical depression made in the cloth showed up badly on-eraslng, anddid not permit complete erasing. Heretoforeit has been practicallyimpossible to use enough grit to give this property, because thequantity necessary would have detracted too much from transparency..Because we are able to improve transparency, we may gofurther inthedirection of using more grit than the prior art would have permitted.The tracing cloth of this invention permits erasing with soft eraserssuch as art gum, and thus there is little if any removal of the coatingsubstance below or laterally of the lines erased. r

vIn compounding the coating composition the components may be varied in.well known ways for the proper qualities. TI'he composition mustexhibit good adherence to the cloth, and be tough enough to retain thegrit well against erasures and drawing forces.-

The following compositions will illustrate the invention.

Exmm: 1 V Ground quartz (300 mesh) ounces 35 Anhydrous ethyl alcoholgallons 2 Stock solution A (see below)-- do 2 Pontacyl fast Blue R grams0.4

Dissolved in anhydrous ethyl alcohol grams" 314 Neutral mineral oil(White Rose, Standard Oil of Indiana) cc 480 Stock solution A Anhydrousethyl alcohol. gallons 20 5 to 6 second nitrocellulose pounds 8 Shellac(dewaxed) do 16 The silica which is preferably of size 300 mesh to startwith, is first ground thoroughly in a ball 2,323,469 ing does not adhereto the glossy back of a basic mill for 12 hours to remove air,- to getthe silica completely wet with the solvent, and to reduce the size ofthe quartz 'still further. Then the stock solution A is added, and theother in-.

gredients. The composition may be coated by a spreader, roll, orlikedevice onto the tracing cloth or paperand the solvent evaporated. Thecomposition of the coating may be varied to get optimum results with anyparticular set of coating conditions or for different bases.

The foregoing example illustrates a lacquer having mineral .oil as arejecta'ble transparentizlng agent. base of thelacquer is practically 2parts of shellac and 1 part of nitrocellulose. Nearly one part ofmineral oil (.85 part) is present.

alcohol base solvent. Such additional coatings have been used inpracticing the invention.

There are other transparentizlng solutions that may be used in thepresent invention.

The use of the term mean that it must be tracing cloth" does not usedfor tracing. The

term is a sort of hang-over from the prior use of prior inferiorproducts, which necessitated Tracing cloth heretofore was transparentfor two reasons. The first one was to permit tracing the desired patternor design onto the cloth. The second was to permit printing by lightthrough the cloth. With the advent of the pres ent.ir1vention providinga transparent medium on which the lines required for printing may bemade originally with pencil, it is now not neces- One reason foremphasizing opacity to reproduce like an ink line in lighton permitsthis drawing in pencil printing. The present inventi on paper or cloth,so that as a progresses, prints of that progress may be obtained priorto final inking, where that is desired. This has the particularadvantage that a design in progress may be sent out to numerousindividuals as blueprints or the like, thus eliminating the necessityfor these individuals and the original draft to be assembled in oneplace.

Wherein we use the term tracing" for a sheet or cloth, we refer to alight-transmitting sheet wherein lines will appear so that the sheet maybe used for reproducing said lines by use of light and light-sensitivesheets.

Wherein we refer to transparentizing agent for the sheet in the lacquerwe do not necessarily mean that it is transferred to the sheet.Reference is made to the description above wherein the mere presence ofit lessens the extraction of transparentizing from the sheet. The agentis thus transparentizing by indirection, but where it is usedon a sheethaving no transparentizing agent before lacquering, it will becomeshared by the sheet and the coating.

The invention may be applied in many ways and is not limited to thespecific illustration. Reference is made to our copending application,Serial No, 283,377, filed July 8, 1939, now Patent No. 2,253,562, issuedAugust 26, 1941, wherein a more complex structure is formed, but inwhich the present invention is' embodied as expressed within the scopeof the appended claims.

We claim:

1. A tracing sheet comprising in combination an original tracing clothof the type which is filled with a hydrophilic colloid andtransparentized with a permanent agent selected from the groupconsisting of oils, fats and waxes; a waterproof transparent lacquercoat on a face of said sheet, said original cloth and said coat bothcontaining the same and a second permanent transparentizing agentselected from the group consisting of oils, fats and waxes, the coatbeing saturated with said second agent, whereby it cannot draw saidsecond transparentizing agent from the clothto diminish the transparencyof the filled cloth.

'2. A tracing sheet comprising in combination an original tracing clothof the type which is filled with a hydrophilic colloid andtransparentized with a permanent agent selected from the groupconsisting of oils, fats and waxes, a waterproof transparent lacquercoat having a nitrocellulose base on a face of said sheet, said originalcloth and said coat both containing the same and a second permanenttransparentizing agent selected from the group consisting of oils, fatsand waxes, said coat being saturated with said second agent, whereby itcannot draw said second transparentizing agent from the cloth todiminish the transparency of the filled cloth.

3. A tracing sheet comprising in combination an original tracing clothof the type which is filled with a hydrophilic colloid andtransparentized with a permanent agent selected from the groupconsisting of oils, fats and waxes, a waterproof transparent lacquercoat having a nitrocellulose base on a face of said sheet, said originalcloth and said coat both containing mineral oil as a second permanenttransparentizing agent, the coat being saturated with said mineral oil,whereby it cannot draw mineral oil from the cloth to diminish thetransparency of the filled cloth.

4. A tracing sheet comprising in combination an original tracing clothof the type which is filled with a hydrophilic colloid andtransparentized with a permanent agent selected irom the groupconsisting of oils, fats and waxes, a waterproof transparent lacquercoat having nitrocellulose and shellac bases on a face of said sheet,laid original cloth and said'coat both containing the same and a secondpermanent transparentizing agent selected from the group consisting ofoils, fats ar-tl waxes, said coat being saturated with said secondagent, whereby it cannot draw said second transparentizing agent fromthe cloth to diminish the transparency of the filled cloth.

5. A tracing sheet/comprising in combination an original tracing clothof the type which is filled with a hydrophilic colloid andtransparentized with a permanent agent selected from the groupconsisting of oils, fats and waxes, a waterproof transparent lacquercoat having nitrocellulose and shellac bases on a face of said sheet,said original cloth and said coat both containing mineral oilas a secondpermanent transparent izing agent, said coat being saturated with saidoil, whereby it cannot draw mineral oil from the cloth. to, diminish"the transparency of the filled cloth.

6. A tracing sheet comprising in combination an original tracing clothof the type which is filled with a hydrophilic colloid andtransparentized with a permanent agent selectedirom the group consistingof oils, fats and'waxes, a waterproof transparent lacquer coat on a faceof said sheet, said original cloth and said coat both containing thesame and a second permanent transparentizing agent selected from thegroup consisting of oils, fats and waxes which second agent has limitedmiscibility with the material of said coat, the coat being saturatedwith said second agent, whereby it cannot draw said second agent fromthe cloth to diminish the transparency of the filled cloth, said coatalso including a grit to provide a tooth for drawing at the surfacethereof. I

7. A tracing sheet comprising in combination an originaltransparentizable fiber sheet, a waterproof transparent lacquer coatone. face of said sheet, said original sheet being transparentized by apermanent agent selected from the group consisting of oils, fats andwaxes which agent has limited miscibility with the material of saidcoat, said coat being saturated with'the said agent, whereby it cannotdraw said agent from the sheet to diminish the transparencyin aging.

8. A tracing sheet comprising in'combination an originaltransparentizable fiber sheet, a waterproof transparent nitrocellul'osebase lacquer coat on a face of said sheet, said original sheet beingtransparentized by a permanent agent selected from the group consistingof oils, fats and waxes which agent has limited miscibility with thesaid coat, the said coat being saturated with the said agent, whereby itcannot draw said agent from the sheet to diminish the transparency inaging.

9. A tracing sheet comprising in combination an originaltransparentizable fiber sheet, a waterproof transparent nitrocellulosebase lacquer coatcoat, said coat being saturated with the mineral oil,whereby it cannot draw mineral oil from the sheet to diminish thetransparency in aging.

10. A tracing sheet comprising in combination an originaltransparentizable fiber sheet, a waterproof transparent lacquer coat ofnitrocellulose and shellac bases on a face of said sheet, said originalsheet being transparentized by a permanent agent selected from the groupconsisting of oils, fats and waxes, said coat being saturated with suchan agent, whereby said coat cannot draw transparentizing agent from thesheet to diminish the transparency in aging.

11. A tracing sheet comprising in combination an originaltransparentizable fiber sheet, a'waterproof transparent lacquer coat ofnitrocellulose and shellac bases on a face of said sheet, said originalsheet being transparentized by mineral oil, said coat being saturatedwith mineral oil, whereby it cannot draw mineral oil from the sheet todiminish the transparency in aging.

12. A tracing sheet comprising in combination an originaltransparentizable fiber sheet, a waterproof transparent lacquer coatcontaining grit for drawing tooth on a face of said sheet, said originalsheet being transparentized by a permanent agent selected from the groupconsisting of oils, fats and waxes, which has limited miscibility withthe material of said coat, said coat being saturated with such an agent,whereby it cannot draw transparentizing agent from' tlre sheet todiminish the transparency in aging.

13. The method of coating a. transparentized tracing sheet of fiber basewhich is filled with a hydrophilic colloid and which contains apermanent transparentizing agent selected from the group consisting ofoils, fats and waxes, which comprises applying a waterproofing lacquerto a face of said sheet, said lacquer containing dissolvedtransparentizing agent for the said filled fiber-base sheet selectedfrom the group consisting of oils, fats and waxes, said agent beingpresent in quantity in excess of the capacity of the dried coatresulting from said lacquer to hold it dissolved therein, whereby it isin part rejected into the sheet in the formation of said coat, andevaporating the said lacquer to provide said coat.

14. The method of coating a transparentized tracing sheet of fiber basewhich is filled with 2.

- hydrophilic colloid and which contains a -perma-' nenttransparentizing agent selected from the group consisting of oils, fatsand waxes, which comprises applying a waterproofing lacquer having anitrocellulose base .to a face of said sheet, said lacquer containingdissolved transparentizing agent for the said filled fiber-base sheetselected from the group consisting of oils, fats and waxes, said agentbeing present in quantity in excess of the capacity of the dried coatresulting from said lacquer to hold it dissolved therein, whereby it isin part rejected into the sheet in the formation of said coat, andevaporating the said lacquer to provide said coat.

15. The method of coating a transparentized tracing sheet of fiber basewhich is filled with a hydrophilic colloid and which contains apermanent transparentizing agent selected from the group consisting ofoils, fats and waxes, which comprises applying a waterproofing lacquerhaving a nitrocellulose base to a face of said sheet, said lacquercontaining dissolved mineral oil in quantity in excess of the capacityof the dried coat resulting from said lacquer to hold it dissolvedtherein, whereby it is in part rejected into the sheet in the formationof said coat, and evaporating the said lacquer to provide said coat.

16. The method of coating a transparentized tracing sheet of fiber basewhich is filled with a hydrophilic colloid and which contains apermanent transparentizing agent selected from the group consisting ofoils, fats and waxes, which rejected into the sheet in the formation ofsaid coat, and evaporating the said lacquer to provide said coat.

17. The method of coating a transparentized tracing sheet of fiber basewhich is filled with a hydrophilic colloid and which contains apermanent transparentizing agent selected from the group consisting ofoils, fats and waxes, which comprises applying a waterproofing lacquerto a face of said sheet, said lacquer containing dissolvedtransparentizing agent for the said filled fiber-base sheet selectedfrom the group consisting of oils, fats and waxes, said agent beingpresent in quantity in excess of the capacity of the dried coatresulting from said lacquer to hold it, whereby it is in part rejectedinto the sheet and in part to the exposed surface of said coat in theformation of the coat, said lacquer also containing in suspension afinely divided grit to give tooth to said exposed surface for drawingthereon and in compensation for the greasy effect resulting from saidrejection of said agent to the surface of the coat, and evaporating thesaid lacquer to provide said coat.

18. The method of making a transparentized tracing sheet oftransparentizable fiber base which comprises applying to a face of saidsheet a waterproofing lacquer containing transparentizing agent for saidsheet selected from the group consisting of oils, fats and waxes, saidagent being present in quantity in excess of the capacity of the driedcoat resulting from said lacquer to hold it, whereby said agent is inpart rejected into the sheet in the formation of the coat, said excessbeing sufiicient both to transparentize the sheet and to provide a coatcontaining said agent dissolved therein at least to the point r ofsaturation, and evaporating the said lacquer to provide said coat.

19. The method of making a transparentized tracing sheet oftransparentizable fiber base which comprises applying to a face of saidsheet a water-proofing lacquer having a base of nitrocellulose andcontaining transparentizing agent for said sheet 'selectedfrom the groupconsisting of oils, fats and waxes, said agent being present in quantityin excess of the capacity of the dried coat resulting from said lacquerto hold it, whereby said agent is in part rejected into the sheet in theformation of the coat, said excess being suificient both totransparentize the sheet and to provide a coat containing said agentdissolved therein at least to the point of saturation, and evaporatingthe said lacquer to provide said coat.

20. The method of making a transparentized tracing sheet oftransparentizable fiber base which comprises applying to a face of saidsheet a. waterproofing lacquer having a base of nitrocellulose andcontaining dissolved mineral oil in quantity in excess of the capacityof the coat resulting from said lacquer to hold it, whereby said mineraloil is rejected in part into said sheet in the formation of said coat,said excess being sufficient both to tra'nsparentize the said sheet andto provide a coat containing mineral oil dissolved therein at least tothe point of saturation, and evaporating the said lacquer to providesaid coat.

21. The method of making a transparentized tracing sheet oftransparentizable fiber base which comprises applying to a face of saidsheet a. waterproofing lacquer having bases of nitrocellulose andshellac and containing dissolved transparentizing agent for said sheetselected from the group consisting of oils, fats and waxes, said agentbeing present in quantity in excess of the capacity of the coatresulting from said lacquer to hold it, whereby said agent is in partrejected into said sheet in the formation of the coat, said excess beingsufficient both to transparentize the sheet and to provide a coatcontaining said agent dissolved therein at least to the point ofsaturation, and evaporating said lacquer to provide said coat.

22. The method of making a transparentized tracing sheet oftransparentizable flber base which comprises applying to a face of saidsheet a waterproofing lacquer having bases of nitrocellulose and shellacand containing dissolved mineral oil in quantity in excess of thecapacity of the coat resulting from said lacquer to hold it, wherebysaid mineral oil is rejected in part into said sheet in the formation ofsaid coat, said excess being sufflcient both to transparentize the saidsheet and to provide a coat containing mineral oil dissolved therein atleast to the point of saturation, and evaporating the said lacquer toprovide said coat.

23. The method of making a transparentized tracing sheet oftransparentizable fiber base which comprises applying to a face of saidsheet a waterproofing lacquer containing dissolved transparentizingagent for said sheet selected from the group consisting of oils, fatsand waxes, said agent beingpresent in quantity in excess of the capacityof the dried coat resulting from said lacquer to hold it, whereby it isin part rejected from the two surfaces of said coat, part into the sheetand part to the exposed surface of the coat, said excess beingsufficient both to transparentize the sheet to provide a, coatcontaining said agent dissolved therein to the point of saturation, andto provide a greasy exposed surface to the coat, said lacquer alsocontaining a grit in suspension to provide tooth to the exposed surfaceof the coat for drawing thereon and in compensation for the saidgreasiness, and

evaporating said lacquer to provide said coat.

WALKER. M. HINMAN.

WALTER G. HOLLMANN.

